Purpose: The 70-gene signature (70-GS) is a prognostic tool, grouping patients in risk groups to assess their need for adjuvant chemotherapy. Tumor cell dissemination to the bone marrow is a marker of minimal residual disease and associated with impaired survival. In this study, we aimed to evaluate whether 70-GS is associated with the presence of disseminated tumor cells (DTCs) in the bone marrow of patients with early breast cancer.
Methods: In patients with hormone receptor-positive HER2-negative early breast cancer, the 70-GS was obtained and the presence of DTCs was immunohistochemically evaluated using cytokeratin staining with the A45-B/B3 antibody.
Results: 149 patients were included into the analysis. 40 (27%) had a high-risk 70-GS and 35 (23%) had detectable DTCs in their bone marrow. 9 (22%) of the 40 patients with high-risk 70-GS and 26 (24%) of the 109 patients with a low-risk 70-GS were positive for DTCs (p = 0.863).
Conclusions: As both 70-GS and DTC detection are known prognostic factors but do not seem to correlate, a follow-up on a larger cohort is warranted to evaluate if a combination of the two is able to better stratify the relapse risk in early breast cancer patients.
Keywords: 70-gene signature; Bone marrow; Breast cancer; Disseminated tumor cells; MammaPrint; Minimal residual disease.